As a probe configuring an ultrasonic diagnostic apparatus for use in the field of medicine, an intracorporeal insertion type ultrasonic probe for carrying out ultrasonic scanning in a body by inserting an ultrasonic transducer into the body cavity of a subject is known.
FIG. 5 is a schematic cross-sectional view showing a structure of a conventional intracorporeal insertion type ultrasonic probe (hereinafter, referred to as a “first conventional example”). An ultrasonic probe having such a structure is described in JP 2001-327501 A, for example. This probe includes an inserting portion 102 to be inserted into a body cavity and a grip portion 101 held by an operator outside of the body cavity. The inserting portion 102 has an elongate rod shape and includes a transducer unit 103 in the vicinity of an end thereof. The inserting portion 102 further includes a swing mechanism for swinging the transducer unit 103. In the first conventional example, the swing mechanism includes a pair of arm members 104 that are arranged in parallel with each other so as to hold the transducer unit 103 therebetween, a connected arm 105 connected to the arm members 104, and a shaft 107 connected to the connected arm 105 via a bevel gear 106. The grip portion 101 includes a motor 108 for generating a driving force for driving the swing mechanism, the motor 108 being connected to the shaft 107. In such an ultrasonic probe, when the motor 108 is driven, the shaft 107 is rotated around an axis of the inserting portion, and this rotating force is transmitted to the connected arm 105 via the bevel gear 106, so that the connected arm 105 is rotated around an axis (hereinafter, referred to as a “swing axis”) orthogonal to the axis of the inserting portion. By the rotation of the connected arm 105, the arm members 104 are advanced and retreated reversely to each other while staying in parallel with each other. As a result, the transducer unit 103 is swung.
However, in the first conventional example, the bevel gear 106 is used as means for converting the rotational movement of the shaft around the axis of the inserting portion into the rotational movement around the swing axis. Therefore, vibrations are likely to be created by contact between gear structures when the swing mechanism is driven. Such vibrations pose a problem of preventing smooth swing movement of the ultrasonic transducer, i.e., smooth ultrasonic scanning, which results in difficulty in obtaining precise ultrasound images.
FIG. 6 is a schematic cross-sectional view showing a structure of another conventional intracorporeal insertion type ultrasonic probe (hereinafter, referred to as a “second convennitonal example”). An ultrasonic probe having such a structure is described in JP 10(1998)-179588 A, for example. This probe includes the inserting portion 102 having the transducer unit 103 and the grip portion 101 having the motor 108 as in the first conventional example. In the second conventional example, the swing mechanism for swinging the transducer unit includes a driving pulley 109 connected to a rotation axis of the motor 108, a driven pulley 111 connected to a swing axis 110 of the transducer unit 103, and a wire 112 connecting these pulleys. In such an ultrasonic probe, when the motor 108 is driven, the driving pulley 109 is rotated, and accordingly the wire 112 is moved. The movement of the wire 112 rotates the driven pulley 111, and then the transducer unit 103 connected to the driven pulley 111 is swung.
As described above, in the second conventional example, the swing mechanism configured by the pulleys and the wire is used. However, since the wire 112 connects the driving pulley 109 provided at the motor 108 in the grip portion 101 and the driven pulley 111 provided at the transducer unit 103 at an end of the inserting portion 102, the wire 112 needs to be long. Accordingly, the wire is likely to become loose, resulting in displacement of the driven pulley, and furthermore displacement of the ultrasonic transducer connected to the driven pulley. Such displacement also makes it difficult to obtain precise ultrasonic images.